Air dryer



Dec. 26, 1967 FIEDLER ETAL A I R DRYER Filed Feb. 16, 1966 United States Patent 3,359,753 AIR DRYER Martin Fiedler, Wooddale, and Guru B. Singh, Cicero,

Ill., assignors to Arrow Tools, Inc., Chicago, [1]., a corporation of Illinois Filed Feb. 16, 1966, Ser. No. 527,975 Claims. (Cl. 62-317) This invention relates generally to an air dryer and more particularly to an air dryer for removing water vapor from a stream of compressed air.

Compressed air is commonly utilized to actuate pneumatic equipment. The pneumatic equipment is usually supplied with air through service lines from a suitable compressor. When the air leaves the compressor it is at a relatively high temperature due to the heat which is generated as the air is compressed. Since the atmosphere contains water vapor, and the capacity of the air to absorb water vapor increases with temperature, the compressed air will contain water vapor. The compressed air is cooled as it is carried through the service lines and used in the operation of pneumatic equipment. The cooled air has a lower capacity for water vapor than the relatively hot air from the compressor. Therefore, the water vapor tends to condense in the service lines and equipment. The condensed water vapor or moisture frequently causes trouble in both the service lines and the pneumatic equipment.

The water vapor may be removed from the compressed air by the use of an air dryer placed between the discharge pipe of the compressor and the service lines. A common type of air dryer utilizes cooling coils to reduce the temperature of the relatively hot compressed air. When the temperature of the air has been reduced below its dew point the water vapor will condense. The condensed Water vapor can then be readily removed from the dryer without damage to service lines and pneumatic equipment.

The volume of air which such a dryer can handle is a direct function of the effective area of the cooling coils. To handle larger volumes of compressed air, prior art dryers merely increased the effectively cooling area by providing larger cooling coils. As a result prior art air dryers having a large capacity are usually very large and bulky. These bulky dryers are not well suited for installation with compressors in locations where the available space is limited.

Therefore, one of the objects of this invention is to provide an efficient air dryer which is relatively compact.

Another object of this invention is to provide an air dryer having a relatively large amount of effective cooling area.

These and other objects and features of the invention will become more apparent from a reading of the following detailed description, taken in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic view of a system for drying compressed air;

FIG. 2 is a detailed sectional view of an air dryer used in the system of FIG. 1 and FIG. 3 is a detailed sectional view of the air dryer along the line 33 of FIG. 2.

Referring now to the drawings in greater detail, there is shown in FIGS. 1 and 2 an air dryer which forms a preferred embodiment of the invention. While being useful in many different fields, the air dryer is intended for use in a system for drying compressed air. When so used, relatively moist compressed air flows into the air dryer 10 through an inlet conduit or tube 12 mounted in a casing 14. The moist compressed air will be cooled and dried within the casing 14, in a manner to be described in greater detail subsequently. The relatively dry air leaves the casing 14 through an air outlet conduit or tube 16 which is positioned at the opposite end of the casing from the inlet conduit 12. The relatively dry air, from the outlet tube or conduit 16 is carried by suitable service lines to pneumatic equipment in which the com pressed air is utilized.

The air dryer 10 is supplied with a liquid coolant or refrigerant through the conduit or tube 18. The liquid coolant flows from the conduit 18 to the helical cooling coil 34 where it vaporizes. The gaseous coolant then leaves the air dryer 10 by means of the tube or conduit 20. The conduit 20 is connected to a suitable compressor 22 which compresses the gaseous coolant to a relatively high pressure. The compressed coolant is then conducted to a condenser 24 by means of a tube 26. The gaseous coolant is condensed, to the liquid state, in the condenser 24. The liquid coolant then flows from the condenser 24 back to the air dryer 10 through a receiver or reservoir 28 and expansion valve 30 by means of a conduit or tube 32. The construction and method of operation of the compressor, condenser, and expansion valve are well known to those skilled in the art and do not per se constitute a part of the invention.

Referring now to FIG. 2, it will be seen that the casing 14, for the air dryer 10, includes a longitudinally extending cylindrical sidewall 36 which is closed at its end portions by two end walls 38 and 40. The helical cooling coil 34 is supported in a coaxial relationship with the casing 14 by the conduits 18 and 20 which extend through apertures in the endwalls 38 and 40. The cooling coil 34 is also supported, in a spaced apart relationship relative to the casing 14, by two support members 42 and 44 which are connected to the sidewall 36 of the casing adjacent to the opposite end walls of the casing. Since the helical cooling coil 34 is positioned substantially coaxial with the casing, it will be apparent that the coil will be positioned with all of its turns equally spaced from the sidewall 36 of the casing.

The helical cooling coil 34 is embedded in a tubular wall 46 which is made of a sintered metal, such as bronze, and contains many small interstices to enable the wall to be permeated by a fluid. The wall 46 has inner and outer surfaces 48 and 50 and are connected at their opposite ends to the two support members 42 and 44. The support members 42 and 44 mount the tubular wall in a spaced apart relationship relative to the sidewall 36 of the casing 14.

The inner surface 50 of the tubular wall 46 defines an air or fluid receiving chamber 52 which is connected at one end portion to the inlet conduit 12. The opposite end portion of the chamber 52 is sealed by the support member 44. From an inspection of FIG. 2, it will be apparent that the conduit 12 extends into the central portion of the tubular wall 46 and is engaged by the inner surface 50 of the wall to form a fluid-tight seal between the inner surface 50 and the conduit 12. Thus the only outlet from the cylindrical chamber 52 is through the orous wall 46, with the direction of fiow being as indicated by the arrows in FIG. 1.

Relatively moist compressed air enters the chamber 52 through the conduit 12. The compressed air will flow through the interstices in the porous tubular wall 46 to a chamber or manifold 54 which is located between casing 14 and the outer surface 4% of the wall 46 (see FIG. 3). The compressed air will then flow from the chamber or manifold 54 through the outlet conduit 16 to service lines and suitable pneumatic equipment. When of compressed air into many smaller streams which will contact the relatively large surface areas of the many small interstices of the wall.

The tubular wall 46 will, due to the many interstices in the wall, have a very large effective cooling area. The heat transfer from the air flowing through the wall will also be improved because the air will be divided into many thin streams which will be quickly cooled by contact with the surface of the interstices. In view of the foregoing remarks, it will be apparent that the tubular wall of a sintered metal provides an extremely large effective cooling surface in a compact space.

Since the cooling coils 34 are embedded in the sintered metal wall 46, there will be extremely efiicient heat transfer between the metal coil and the wall which is fused to the coil. Therefore, the compressed air will, by flowing through the tubular wall 46, be cooled to a low temperature. When the compressed air is cooled to a low temperature, the dew point of the air will be lowered, and the Water vapor carried by the air Will be condensed and deposited within the casing 14 of the air dryer 19. A suitable drain fitting or conduit is connected to the casing 14 to carry away the condensed moisture from the compressed air.

For purposes of affording a more complete understanding of the invention, it is advantageous to provide a functional description of the method in which the Component parts cooperate. Relatively moist compressed air is conducted to the air dryer by means of the conduit 12. The air flows through the conduit 12 into a central chamber 52 which is located within a porous wall 46 of a sintered metal. The wall 46 is cooled by means of a cooling coil 34 through which a suitable refrigerant flows.

The compressed air will permeate through interstices in the wall 46 to the surrounding chamber or manifold 54. In flowing through the wall the compressed air will be divided into many small thin streams by the interstices in the wall. These small streams of compressed air will contact the extremely large surface area of the many interstices in the wall. Thus, the elfective cooling area of the embedded cooling coil 34 will be greatly increased by the sintered metal wall 46. After the moist warm air contacts the many cooling surfaces of the sintered metal wall, the air will be cooled below its dew point and Water vapor will be condensed from the air. The cool, relatively dry air will then flow out the inlet tube or conduit 16.

The cooling coil 34 is supplied with coolant or refrigerant by means of a compressor 22 and condenser 24. The liquid coolant or refrigerant will flow from the condenser 24 to the reservoir 28 and expansion valve 39. The expansion valve 30 will enable the liquid coolant to vaporize in the cooling coil 34. The heat of vaporization will be absorbed by the liquid coolant, during vaporization, from the sintered metal wall 46 and the warm compressed air flowing through the wall. The vaporized coolant or refrigerant is then conducted back to the compressor 22 by means of an outlet tube or conduit 20.

The tubular wall 46 has been shown as being closed at one end by the support member 44. Although this facilitates the embedding of the coil 34 in the sintered metal wall, it is contemplated that a bottom wall of sintered metal could be utilized to close the end of the tubular wall 46. If such a sintered metal end wall Were integrally formed with the tubular wall 45, it will be apparent to those skilled in the art that the effective cooling area of the tubular wall 46 would be increased. It is also contemplated that the direction of air flow through the wall 46 could be reversed. Various other changes in structure will, no doubt, occur to those skilled in the art; and these changes are to be understood as forming a part of this invention insofar as they fall within the spirit and scope of the appended claims.

What is claimed is:

1. An air dryer comprising a casing defining first chamber means, a tubular wall of a permeable sintered metal mounted in said first chamber means, second chamber means Within said tubular wall of sintered metal, a cooling coil embedded in said tubular wall of sintered metal, a first fluid conduit means connected to said second chamber means and extending through said first chamber means, a second fluid conduit means connected to said first chamber means, said wall of permeable sintered metal enabling a stream of fluid to flow between said first and second conduit means through said tubular wall, a third conduit means connected to one end of said cooling coil, a fourth fluid conduit means connected to an opposite end of said cooling coil, and a fluid chamber means in said cooling coil to enable a coolant to flow from said third fluid conduit means to said fourth conduit means to cool said wall of sintered metal and the fluid flowing through said wall, said first fluid conduit means extending into said second chamber means and being engaged by an inner surface of said tubular wall of sintered metal.

2. An air dryer as set forth in claim 1 wherein said second chamber extends for substantially the entire length of said tubular wall of a permeable sintered metal.

3. An air dryer as set forth in claim 2 wherein said cooling coil extends for substantially the entire length of said tubular wall of permeable sintered metal and said cooling coil, tubular wall of permeable sintered metal, and second chamber means are all mounted in a substantially coaxial relationship.

4. An air dryer as set forth in claim 1 further including a compressor means to compress said coolant in its gaseous state, a condenser means connected to said compressor means to condense said gaseous coolant to a liquid state, and an expansion valve means connected to said condenser means and said third fluid conduit means to enable said coolant to evaporate in said heli-.

cal cooling coil, said helical cooling coil being connected to said compressor by said fourth fluid conduit means.

5. An air dryer comprising a casing defining first chamber means, a tubular wall of a permeable sintered metal mounted in said first chamber means, second chamber means within said tubular Wall of sintered metal, a cooling coil embedded in said tubular Wall of sintered metal, a first fluid conduit means connected to said second chamber means and extending through said first chamber means, a second fluid conduit means connected to sai first chamber means, said wall of permeable sintered metal enabling a stream of fluid to flow between said first and second conduit means through said tubular wall, a third conduit means connected to one end of said cool ing coil, a fourth fluid conduit means connected to an opposite end of said cooling coil, and a fluid chamber means in said cooling coil to enable a coolant to flow from said third fluid conduit means to said fourth conduit means to cool said wall of sintered metal and the fluid flowing through said wall, said first chamber means including longitudinally extending sidewall means, and a first and second end wall means connected to said longitudinally extending sidewall means, said tubular wall of sintered metal being mounted in a spaced apart relationship relative to said side wall and end Walls so that said first chamber means completely encloses said tubular wall of sintered metal.

References Cited UNITED STATES PATENTS 2,187,470 1/1940 Collins 62283 2,375,069 5/1945 Bennett 623 17 2,401,797 6/1946 Rosmussen 210- 2,624,554 1/1953 Morrison 62437 2,740,268 4/1956 .lones 62-317 WILLIAM J,- WYE, Primary Examiner. 

1. AN AIR DRYER COMPRISING A CASING DEFINING FIRST CHAMBER MEANS, A TUBULAR WALL OF A PERMEABLE SINTERED METAL MOUNTED IN SAID FIRST CHAMBER MEANS, SECOND CHAMBER MEANS WITHIN SAID TUBULAR WALL OF SINTERED METAL, A COOLING COIL EMBEDDED IN SAID TUBULAR WALL OF SINTERED METAL, A FIRST FLUID CONDUIT MEANS CONNECTED TO SAID SECOND CHAMBER MEANS AND EXTENDING THROUGH SAID FIRST CHAMBER MEANS, A SECOND FLUID CONDUIT MEANS CONNECTED TO SAID FIRST CHAMBER MEANS, SAID WALL OF PERMEABLE SINTERED METAL ENABLING A STREAM OF FLUID TO FLOW BETWEEN SAID FIRST AND SECOND CONDUIT MEANS THROUGH SAID TUBULAR WALL, A THIRD CONDUIT MEANS CONNECTED TO ONE END OF SAID COOLING COIL, A FOURTH FLUID CONDUIT MEANS CONNECTED TO AN OPPOSITE END OF SAID COOLING COIL, AND A FLUID CHAMBER MEANS IN SAID COOLING COIL TO ENABLE A COOLANT TO FLOW FROM SAID THIRD FLUID CONDUIT MEANS TO SAID FOURTH CONDUIT MEANS TO COOL SAID WALL OF SINTERED METAL AND THE FLUID FLOWING THROUGH SAID WALL, SAID FIRST FLUID CONDUIT MEANS EXTENDING INTO SAID SECOND CHAMBER MEANS AND BEING ENGAGED BY AN INNER SURFACE OF SAID TUBULAR WALL OF SINTERED METAL. 